Hey - if you create a non-hosted shopping cart button by unchecking "Save button at PayPal" in Step 2, you can later alter the code manually and add text boxes. After creating the button, you need to press "Remove code protection", and then copy and paste the code into a text editor.
If you already have two text boxes, you'll see a section of code that looks something like this:
<table>
<tr><td><input type="hidden" name="on0" value="Enter Name">Enter Name</td></tr><tr><td><input type="text" name="os0" maxlength="200"></td></tr>
<tr><td><input type="hidden" name="on1" value="Enter Phone Number">Enter Phone Number</td></tr><tr><td><input type="text" name="os1" maxlength="200"></td></tr>
</table>
The first text box is represented by the section between the blue-highlighted code; the second text box is represented by the section between the red-highlighted code. To add a third text box, paste an identical section of code between the second text box and the line that reads </table> at the end of the code above. Then, you need to edit the label that appears twice in the code for the new text box (e.g. "Enter Phone Number") so that the new text box is labeled apprpriately. Further, you need to change "on1" to "on2" and "os1" to "os2" to create this third text box.
Similarly, to add a fourth text box, you would again copy the code from one of the above text boxes, paste it directly above </table>, edit the two labels within the code, and this time write "on3" in place of "on2" and "os3" in place of "os2". Those numbers are counters and start at 0 for the first text box.
When you test your full, updated button code, it should display multiple text boxes. You should probably also test the new button to be sure it captures information from all four test boxes before implementing it on your site; for example, it won't help to display four text boxes if PayPal only captures and records the information the user types into the first two, but not the third and fourth. I hope this helps.
